Synthesis and purification of single-walled carbon nanotubes by methane decomposition over iron-supported catalysts

Abstract

This article describes the synthesis and the purification of carbon nanotubes. Large quantities of single-walled carbon nanotubes (SWNTs) with few defects and very small amount of amorphous carbon coating have been synthesized by catalytic decomposition of methane over well-dispersed iron particles supported on MgO at the temperature range from 800 to 1000 degrees C. It was found that the quality of carbon nanotubes was slightly increased as increasing growth temperature while the yield was decreased to some degree. It was also found that the as-grown SWNTs can be separated easily from the support by a simple acidic treatment rather than thermal oxidation to obtain a product with high yields of SWNTs. Above 94 wt % high purity SWNTs were obtained by combining two-step processes of thermal oxidation in air and acid treatment without multistep filtration. The as-grown and purified SWNTs were also characterized by field emission scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. (c) 2006 American Vacuum Society.